/* 元素从无到有，刚开始 */
.xw-enter,
.xw-appear {
  opacity: 0;
}

/* 从无到有的过程中 */
.xw-enter-active,
.xw-appear-active {
  opacity: 1;
  transition: all 300ms;
}


/* 从有到无 */
.xw-exit {
  opacity: 1;
}

/* 从有到无的过程中 */
.xw-exit-active {
  opacity: 0;
  transition: all 300ms;
}